The present invention relates to a surface mount crossover component for use as a discrete component in an integrated circuit where two signal lines cross one another, and in particular, a surface mount crossover component for use in an integrated circuit where an RF signal line crosses a DC line.
There are many instances in the design of integrated circuits where signal lines must cross one another. In the field of wireless communications, for example, an integrated circuit includes RF signal lines and DC lines, wherein the RF lines carry the communication signal and the DC line controls and supplies power to solid state components of the circuit, such as semiconductor amplifier components.
It is known that the RF signal carried by the RF line is adversely affected by the presence of the DC current carried by the DC line at points where the two lines approach one another, and especially where the two lines cross one another. Accordingly, many attempts have been made to isolate the two lines from one another. One example of isolating the lines when they cross one another is disclosed in U.S. Pat. 5,321,375, which describes an RF crossover network that includes an RF line capacitively coupled to an overlying DC line through an interposed dielectric layer. The problem with this crossover network, however, is that the structure of the DC line must be controlled precisely to insure the appropriate capacitive coupling between the DC line and the RF line. Such precise control inevitably makes the device more difficult to manufacture, and consequently increases the cost of production.
Other attempts to isolate RF and DC lines from one another have been incorporated in the design of the overall integrated circuit board. The ""375 patent explains that it is common in the design of integrated circuit boards to incorporate multi-layer substrate techniques when building the circuit board itself, wherein the DC lines for the integrated circuit are formed on one dielectric layer, and the RF signal lines are formed on a different dielectric layer to provide electrical isolation between the two lines. It is also common, as explained in the ""375 patent, to incorporate a ground plane within the multi-layer integrated circuit board to provide capacitive isolation between the DC lines and the RF signal lines. The ""375 patent explains, however, that such multi-layer integrated circuit boards are time consuming and costly to produce, and require more material as a result of the separate ground plane provided within the circuit board between the DC lines and RF signal lines.
Another problem with this conventional technique, however, is that the designer is required to plan and arrange the DC lines for the entire integrated circuit board with respect to the location of the RF signal lines formed on another layer within the integrated circuit board. Accordingly, the layout of the overall circuit board is often dictated by the locations of the DC lines and RF signal lines.
It would be desirable to provide a surface mount crossover component that can be used at discrete locations anywhere on an integrated circuit board where two crossing conductor lines need to be isolated from one another. To date, however, there is no such surface mount crossover component available.
It is an object of the present invention to provide a surface mount crossover component that overcomes the disadvantages of the prior art.
It is another object of the present invention to provide a surface mount crossover component that provides sufficient electrical and capacitive isolation between two crossing conductor lines and can be manufactured easily and inexpensively.
To achieve these objects, a first embodiment of the present invention is a surface mount crossover component that is used to cross one conductor line over another conductor line that is already printed on an integrated circuit. The surface mount crossover component in accordance with this embodiment comprises a lowermost first dielectric layer, a ground plane layer disposed above the first dielectric layer, a second dielectric layer disposed above the ground plane layer, and a conductor line disposed above the second dielectric layer. The conductor line traverses the second dielectric layer to provide an electrical path from one end of the crossover component to an opposed end thereof. The dielectric layers and the ground plane layer electrically and capacitively isolate, respectively, the conductor lines from one another. Accordingly, current, such as an RF signal, can flow through the component via the conductor line without interference from current, such as a DC control signal, flowing through the conductor line printed on the integrated circuit.
A second embodiment of the present invention is a surface mount crossover component that is used to cross one conductor line over another conductor line formed in another functional surface mount component. The surface mount crossover component in accordance with the second embodiment comprises a functional surface mount component, a ground plane layer disposed on one of opposite major surfaces of the functional surface mount component, a dielectric layer disposed adjacent the ground plane layer, and a conductor line disposed adjacent the dielectric layer. The conductor line traverses the dielectric layer to provide an electrical path from one end of the crossover component to an opposed end thereof. The dielectric layer and the ground plane layer electrically and capacitively isolate, respectively, the conductor line from the conductor lines of the functional surface mount component. Accordingly, current can flow through the component via the conductor line without interference from current flowing through the conductor lines of the functional surface mount component.
A third embodiment of the present invention is a surface mount crossover component that is used to cross two conductor lines over one another within the body of the crossover component itself. The surface mount crossover component in accordance with the third embodiment comprises first and second conductor lines that are electrically and capacitively isolated from one another by an interposed ground plane.
A preferred form of the third embodiment includes a bottom ground plane layer, a first dielectric layer disposed above the bottom ground plane layer, a first conductor line disposed above the first dielectric layer, a second dielectric layer disposed above the first conductor line, an internal ground plane layer disposed above the second dielectric layer, a third dielectric layer disposed above the internal ground plane layer, a second conductor line disposed above the third dielectric layer, a fourth dielectric layer disposed above the second conductor line, and a top ground plane layer disposed above the fourth dielectric layer. The surface mount crossover component in accordance with this preferred embodiment of the present invention allows a first signal to be transmitted through the component via one of the first and second conductor lines with no substantial interference from a second signal transmitted via the other one of the first and second conductor lines. As with the other embodiments, the signals passing through the first and second conductor lines, respectively, are electrically and capacitively isolated from one another so that the presence of current passing through one of the conductor lines (e.g., DC current passing through a DC control line) does not interfere with the signal passing through the other conductor line (e.g., an RF signal passing through an RF line).
As used herein, the phrase xe2x80x9csurface mount componentxe2x80x9d means a component that is to be mounted on a printed, integrated circuit board having printed circuit traces on at least one surface of the board. A surface mount component has termination contacts that are connected to the printed circuit traces by soldered connections between the terminals and the printed circuit traces. Unlike non-surface mount techniques, surface mount components typically do not include leads that extend through holes in the printed circuit board. As such, surface mount components are particularly well suited for automatic assembly. Surface mount components are mounted on continuous tapes formed into reels that are used by automatic assembly equipment to place the components on the printed circuit board. Typically, the components are temporarily attached to the board with an adhesive, solder paste, or the like prior to soldering, and then soldered in a single operation with the other surface mount components.
These and other features and advantages of the present invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings.